Process for the conversion to sulfur and/or sulfur dioxide of other sulfur compoundsand catalysts therefor



Patented July 3, 1951 PROCESS FOR THE CONVERSION TO SUL- FUR AND/ORSULFUR DIOXIDE OF OTHER SULFUR COMPOUNDS AND CATALYSTS THEREFOR PaulXavier Spillane, Abbotsi'ord, near Sydney, New South Wales, Australia,asslgnor to Keith Williams, Sydney, New South Wales, Australia NDrawing. Application July 21, 1949, Serial No. 106,096. In Australia May31, 1946 8 Claims. 1

This application is a continuation-in-part of my application Serial No.743,188 filed April 22, 1947, now abandoned.

This invention is directed .to a process for catalytically oxidisinghydrogen sulphide to elemental sulphur and/or sulphur dioxide, and tocatalysts for use in such process. In some cases the catalysts can alsobe used to effect catalytic oxidation of carbon oxysulphide and carbondisulphide and other organic sulphur compounds to sulphur and/or sulphurdioxide.

According to the invention which is the subject of applicant's priorapplication No. 60,378 gaseous sulphides, including hydrogen sulphide,can be catalytically oxidised to elemental sulphur, or mixtures ofelemental sulphur and sulphur dioxide by passing the gaseous sulphidestogether with oxygen, carbon monoxide, or carbon dioxide over a new ironcatalyst. The iron catalyst of that invention is prepared from a mixtureof alkali carbonate and iron oxide by first reducing the iron oxide tocatalytically active metallic iron and then passing a gaseous sulphidethereover until the alkali and iron are completely converted to sulphideand become capable of carrying out the process. It is essential to thatinvention that the iron oxide be first reduced to the catalyticallyactive metallic iron.

I have now discovered that hydrogen sulphide can be catalyticallyoxidised to elemental sulphur, or mixtures of elemental sulphur andsulphur dioxide, by catalysts consisting of mixtures of an alkalisulphide and sulphides of metals selected from the group consisting ofnickel, cobalt, manganese, tin and aluminum, the said sulphides beingprepared in situ upon a catalyst carrier by the action of a mixture ofhydrogen and hydrogen sulphide upon mixtures of alkali compounds andreducible compounds of the said metals.

Accordingly, this invention is directed to a catalytic oxidation processfor converting hydrogen sulphide to sulphur or mixtures of sulphur andsulphur dioxide comprising contacting hydrogen sulphide and a gasselected from the group consisting of oxygen and/or oxides of carbon ata temperature from 80 C. to 400 C. with a catalyst composed of an alkalisulphide and a sulphide of a metal selected from the group consisting ofnickel, cobalt, manganese, tin and aluminium in which the proportion ofalkali sulphide is from 5% to 66% of the metal sulphide, said catalysthaving been formed by passing a mixture of hydrogen sulphide andhydrogen over an intimate admixture upon a catalyst carrier supplied assuch, or in the combined form as carbon monoxide or carbon dioxide.

The catalyst contains as its active constituents alkali sulphides andsulphides of at least one metal selected from the group consisting. ofnickel, cobalt, manganese, tin and aluminum. The physical form of thecatalyst, and the manner in which the'metal sulphide is formed, are bothimportant. The alkali sulphides and the metal sulphides must be inintimate admixture, and the mixture must be distributed over a catalystcarrier to provide an efllcient catalyst. The catalytically active metalsulphide must be produced along with the alkali sulphide by reducing ametal compound in the presence of hydrogen sulphide, whereby a doublereaction occurs in which the desired sulphide is produced. The reducinggas and the hydrogen sulphide are contacted with the partially preparedcatalyst at a temperature in the region of 240 C. until all the alkaliand metal are converted to the sulphide. The procedure outlined isnecessary to prevent the formation of forms of the metal sulphideinactive in the present process.

Several different methods can be employed to prepare the catalyst. Inall methods, however, an intimate admixture of one or more alkalicompounds (preferably as the carbonate, bicarbonate, sulphite orsulphide) and one or more reducible compounds of the metals enumeratedabove is formed on a catalyst carrier. This intimate admixture may beobtained by dry mixing and grinding the alkali compound or compounds,metal compound or compounds, and inert catalyst carrier together to aline powder, and subsequently mixing to a paste with a solvent, such aswater, for the alkali compound. This method is particularly applicablewhen starting with manganese dioxide, nickel oxide and cobalt oxide.

An alternative method is to melt the metal compound and thoroughly stirthe catalyst carrier into it to give a stiff paste. The paste may beheated to decompose the metal compound to the oxide in those cases whereheating will cause such decomposition, as in the case of manganicnitrate. Alternatively, the paste may be allowed to cool. The resultantpaste is then immersed in a strong solution of the alkali compound,preferably until saturated, then dried and/or baked, and granulated intopellets.

Another method of obtaining the desired intimate admixture is to employwater-soluble salts of the metal or metals. The catalyst carrier,preferably in pellet form, is immersed in the metal compound solutionuntil saturated, then dried, for example at a temperature between 110 C.and 200 C., then immersed in an alkali salt solution, and dried again.

The catalyst may be converted to pellet form, for use ina catalystchamber, at any suitable stage of the preparation.

Having formed the intimate admixture of an alkali compound and areducible compound of a metal from the selected group upon the carrierthe partly prepared catalyst, in pellet or other suitable form, ispacked into a chamber, and a mixture of a reducing gas and hydrogensulphide is passed into contact therewith. At first substantially allthe hydrogen sulphide is removed from the gas with the conversion of thealkali and metal compounds to the sulphides. After a time the partlyprepared catalyst reaches a stage where it will no longer remove thehydrogen sul- 1 phide from the gas and hydrogen sulphide ap-- pears inthe efiiuent gases from the chamber. The passage of thehydrogen-sulphide-reducing gas mixture over the partly prepared catalystis continued for a further period of up to two hours.

If the reducing gas is carbon monoxide or water gas, then it will befound that the hydrogen sulphide gradually disappears from the efliuentgas, and elemental sulphur, or elemental sulphur and sulphur dioxide,appear. The catalyst is now ready for use in the process of thisinvention. In carrying out the process of this invention hydrogensulphide is mixed with oxygen, carbon monoxide or carbon dioxide, andthe mixture passed into contact with the catalyst prepared as above at atemperature above 80 C. If the process is carried out at below 260 C.,and the catalyst has never, at any time, exceeded that temperature, thenthe hydrogen sulphide is converted to elemental sulphur. If the processis carried out at above260 C., or if the catalyst has at some timeexceeded that temperature, then some of the hydrogen sulphide will beconverted to sulphur dioxide, and both elemental sulphur and sulphurdioxide will be obtained.

Catalysts containing nickel, cobalt or tin sulphide are capable ofoxidising carbon disulphide and carbon oxysulphide, as well as hydrogensulphide, to sulphur or mixtures of sulphur and sulphur dioxide. Carbondisulphide and carbon oxysulphide may also replace hydrogen sulphide inthe preparation of catalysts in which the selected metal is nickel,cobalt or tin.

The catalyst may include more than one alkali sulphide, and may includesulphides of more than one metal.

If the process of this invention is carried out under oxidisingconditions the alkali sulphide in the catalyst is rapidly converted toalkali sulphite, but the process remains effective despite the change.

Examples of suitable catalyst carriers are diatomaceous earth,kieselguhr, pumice, activated charcoal and silica gels.

Cyanide compounds, tar fog or heavy petroleum fog, if present in thesulphur-containing materials to be treated, must be removed beforesubjecting the materials to the process of this invention. It isbelieved that the cyanide compounds, if not removed, are taken up by thealkali sulphide in the catalyst. Whatever the reaction, the cyanidecompounds or the fogs adversely affect the efficiency of the catalyst,and should be removed beforehand.

A more detailed description of the preparation of the catalyst of thisinvention will now be given with the aid of examples.

Example 1 A catalyst carrier such as kieselguhr in pellet form isimmersed in a solution in water of nickel sulphate (Ni2SO4) untilsaturated. The pellets are then dried by heat at about 110-200 C., areimmersed in a solution of alkali carbonate of approximately 16% solutionuntil saturated, and the pellets again dried by heat. The pellets areloaded into a catalyst chamber and a gaseous mixture comprising hydrogensulphide and hydrogen is passed into contact therewith at approximately240 C. until the hydrogen sulphide is no longer taken up and appears inthe aflluent gases and for two hours thereafter.

The catalyst so obtained comprises an intimate mixture of nickelsulphide (NizSa) and alkali sulphide. The alkali sulphide may beconverted to alkali sulphite if oxygen is present in the gasessubsequently treated by this catalyst.

The gaseous mixture employed in preparing the catalyst may includecarbon disulphide, or carbon oxysulphide in place of, or together with,the hydrogen sulphide, whilst the hydrogen may be replaced by carbonmonoxide or any commercial reducing gas such as water gas. If thereducing gas contains carbon monoxide completion of the catalystpreparation is indicated by the appearance of sulphur in the eiiluent.gases.

Example 2 The method disclosed in Example 1 is carried out with cobaltsulphate (C02SO4) in place or the nickel sulphate.

Example 3 Two parts of manganic nitrate by weight are I melted and mixedwith suflicient kieselguhr or Erample 4 The method of preparation ofExample 1 is carried out employing alkali sulphite in place 0! alkalicarbonate.

Example 5 The method of preparation of Example 1 is carried outemploying alkali sulphide in place of alkali carbonate.

Example 6 The method of preparation of Example 1 is carried outemploying ,manganic sulphate or manganic nitrate in place of nickelsulphate.

Example 7 The method of preparation of Example 1 is carried outemploying stannic sulphate in place of nickel sulphate.

Example 8 r The method of preparation of Example 1 is carried outemploying aluminium sulphate in place of nickel sulphate.

Example 9 Ordinary town gas containing 250 grains hydrogen sulphide per100 cubic feet and 20 grains of organic sulphur compounds (consisting ofcarbon disulphide, thiophene, carbon oxysulphide and mercaptans) arepassed into contact with a catalyst prepared in accordance with Example1 at a. space velocity of approximately 500 and at a temperature of240-260 C. The exit gases contain elemental sulphur, mercaptans, andthiophene. The whole of the hydrogen sulphide, the carbon disulphide andthe carbon oxysulphide is converted to the elemental sulphur.

The catalyst used in this example can be replaced by either of thoseprepared as described in Examples 2 and 7.

Example Coke oven gas containing 200 grain of hydrogen sulphide and 6grains of organic sulphur compounds per 100 cubic feet is treated forthe production of elemental sulphur. The organic sulphur content isregarded as unimportant in this gaseous mixture. A manganese catalystprepared in accordance with Example 3 is used and the gas passed intocontact therewith at a space velocity of 500 and at a temperature of 260C. The exit gases contain elemental sulphur, 6 grains per 100 cubic feetorganic sulphur compounds and 4 grains of hydrogen sulphide per 100cubic feet of exit gas. This represents a 98% conversion of the originalhydrogen sulphide to elemental sulphur.

The catalyst used in the above example may be replaced by any of thecatalysts prepared as described in Examples 3, 4, 5, 6 or 8.

Having thus disclosed the invention, what is claimed is:

.1. A catalytic oxidation process for converting gaseous sulphide tosulphur or mixtures of sulphur and sulphur dioxide, which comprisescontacting the gaseous sulphide and a gas selected from the groupconsisting of oxygen and oxides of carbon at a temperature between 80 C.and 400 C. with a catalyst comprising an alkali sulphide and a sulphideof a metal selected from the group consisting of nickel, cobalt,manganese, tin and aluminium in which the proportion of alkali sulphideis from 5% to 66% of the metal sulphide, said catalyst having beenformed by passing a mixture of the gaseous sulphide and a reducing gasselected from the group consisting of. hydrogen, carbon monoxide andwater gas over an intimate mixture upon a catalyst carrier of an oxideof the selected metal and a'member selected from the group consisting ofalkali carbonate, alkali bicarbonate, alkali sulfide and alkali sulflte,whereby in said oxidation process the gaseous sulphide i converted intoelemental sulphur when the temperature of the oxidation process does notexceed 260 C. and the catalyst has at no time been heated to atemperature exceeding 260 C., and is converted into a mixture of sulphurand sulphur dioxide when the temperature of the oxidation processexceeds 260 C. and when the catalyst has at any time been heated to atemperature exceeding 260 C.

2. A process according to claim 1. wherein the gaseous sulphide isselected from the group consisting of hydrogen sulphide, carbondisulphide and carbon oxysulphide, and the metal sulphide is nickelsulphide.

3. A process according to claim 1, wherein the gaseous sulphide isselected from the group consisting of hydrogen sulphide, carbondisulphide and carbon oxysulphide, and the metal sulphide is cobaltsulphide.

4. A process according to claim 1, wherein the gastous sulphide isselected from the group consisting of hydrogen sulphide, carbondisulphide and carbon oxysulphide, and the metal sulphide is tinsulphide.

5. A process according to claim 1, wherein the gaseous sulphide ishydrogen sulphide and the metal sulphide is manganese sulphide.

6. A process according to claim 1, wherein the gaseous sulphide ishydrogen sulphide and the metal sulphide is aluminium sulphide.

7. A catalytic oxidation process for converting gaseous sulphide tosulphur, which comprises contacting the gaseous sulphide and a. gasselected from the group consisting of oxygen and oxides of carbon at atemperature between C. and 260 C. with a catalyst comprising an alkalisulphide and a sulphide of a. metal selected from the group consistingof nickel, cobalt, manganese, tin and aluminium in which the proportionof alkali sulphide is from 5% to 66% of the metal sulphide, saidcatalyst having been formed by passing a mixture of the gaseous sulphideand a reducing gas selected from the group consisting of hydrogen,carbon monoxide and water gas over an intimate mixture upon a catalystcarrier of an oxide of the selected metal and a, member selected fromthe group consisting of alkali carbonate, alkali bicarbonate, alkalisulfide and alkali sulfite at a temperature of about 240 C.

8. A catalyst comprising an alkali sulphide and a sulphide of a metalselected from the group consisting of nickel, cobalt, manganese, tin andaluminium in intimate admixture upon a catalyst carrier and in which theproportion of alkali sulphide is from 5% to 66% of the metal sulphide,said catalyst having been formed by passing a mixture of gaseoussulphide and a reducing gas selected from the group consisting ofhydrogen, carbon monoxide and water gas over an intimate admixture uponthe said carrier of an oxide of the selected metal and a member selectedfrom the group consisting of alkali carbonate, alkali bicarbonate,alkali sulphide and alkali sulphite, said catalyst being an active agentat a temperature between 80 C. and 400 C. for the catalytic oxidation ofgaseous sulphides to elemental sulphur when the catalyst is at no timeheated to a temperature exceeding 260 C. and to a mixture of sulphur andsulphur dioxide when the catalyst is at any time heated to a temperatureexceeding 260 C.

PAUL XAVIER. SPILLANE.

REFERENCES CITED The following reierences'are of record in the file ofthis patent:

UNITED STATES PATENTS Signaigo June 25, 1946

1. A CATALYTIC OXIDATION PROCESS FOR CONVERTING GASEOUS SULPHIDE TOSULPHUR OR MIXTURES OF SULPHUR AND SULPHUR DIOXIDE, WHICH COMPRISESCONTACTING THE GASEOUS SULPHIDE AND A GAS SELECTED FROM THE GROUPCONSISTING OF OXYGEN AND OXIDES OF CARBON AT A TEMPERATURE BETWEEN 80*C. AND 400* C. WITH A CATALYST COMPRISING AN ALKALI SULPHIDE AND ASULPHIDE OF A METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL,COBALT, MANGANESE, TIN AND ALUMINIUM IN WHICH THE PROPORTION OF ALKALISULPHIDE IS FROM 5% TO 66% OF THE METAL SULPHIDE, SAID CATALYST HAVINGBEEN FORMED BY PASSING A MIXTURE OF THE GASEOUS SULPHIDE AND A REDUCINGGAS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, CARBON MONOXIDE ANDWATER GAS OVER AN INTIMATE MIXTURE UPON A CATALYST CARIER OF AN OXIDE OFTHE SELECTED METAL AND A MEMBER SELECTED FROM THE GROUP CONSISTING OFALKALI CARBONATE, ALKALI BICARBONATE, ALKALI SULFIDE AND ALKALI SULFITE,WHEREBY IN SAID OXIDATION PROCESS THE GASEOUS SULPHIDE IS CONVERTED INTOELEMENTAL SULPHUR WHEN THE TEMPERATURE OF THE OXIDATION EROCESS DOES NOTEXCEED 260* C. AND THE CATALYST HAS AT NO TIME BEEN HEATED TO ATEMPERATURE EXCEEDING 260* C., AND IS CONVERTED INTO A MIXTURE OFSULPHUR AND SULPHUR DIOXIDE WHEN THE TEMPERATURE OF THE OXIDATIONPROCESS EXCEEDS 260* C. AND WHEN THE CATALYST HAS AT ANY TIME BEENHEATED TO A TEMPERATURE EXCEEDING 260* C.